Refrigerating apparatus



March 11, 1941. Q Q PEARCE 2,234,740

REFRIGERATING APPARATUS Filed Jan. 50, 1934 a Sheets-Sheet 1 122 4 75I/llop A23 99 97 I02 IN y MZJ EYS March 11, 1941. c PEARCE 2,234,740

REFRIGERAT ING APPARATUS Filed Jan. 50, 1934 6 Sheets-Sheet 2 INVENTORlme/ BY z ATTORNEYS March 11, 1941. c PEARCE 2,234,740

REFRIGERAT ING AP PARATU S Filed Jan. 30, 1934 6 Sheets-Sheet 6 5 4 5@fl/ZMV adv/W Patented Mar. 11, 1941 PATENT OFFICE 2,234,740REFRIGERATING APPARATUS George C. Pearce, Dayton, Ohio, assignor toGeneral Motors Corporation, Dayton, Ohio, a corporation of DelawareApplication January 30, 1934, Serial No. 708,993

21 Claims.

partment as well as for freezing ice cubes and comestibles. In order toserve this dual purpose, the temperature of the evaporating means is unecessarily something of a compromise. In order to freeze ice cubes andc'omestibles, it is necessary to operate the refrigerating system atfreezing temperatures. This causes moisture to condense and collect uponthe evaporator or cooling unit in the form of frost. This frost acts asan insulator and prevents the eflicient transfer of heat between thefood compartment air and the evaporator.

, It has been customary to instruct the user of a refrigerator toperiodically shut down the refrigerating apparatus in order to permitthe frost to melt from the cooling unit. This, however, is ratherinconvenient and if not carefully attended, the refrigerating apparatusmay be kept shut down for too long a time, thus permitting thetemperatures within the food compartment to rise sufliciently high topermit food spoilage. 7

It is an object of my invention to provide a refrigerating apparatuswherein a common control means is provided for continuous cycling of therefrigerating apparatus to maintain the evaporating means either atfreezing temperatures or temperatures sufficiently high to permitdefrosting of the evaporator and yet provide adequate cooling of thefood compartment so as to prevent food spoilage.

It is a further object of my invention to provide a refrigerating systemhaving a control means for cycling the refrigerator between given highand low limits which is further provided with an adjusting meansoperated by a single knob' and dial which, under the control of theknob, will provide cycling at other temperature limits below freezingwith the differential between the high and low limits remaining thesame, as well as means under the control of the knob for providingcontinuous cycling with the differential between the high and low limitswidened and with the upper limit being a sufficient amount abovefreezing to cause defrosting of the evaporator or cooling unit and topermit continuous cycling of the refrigerating system without thecollection of frost.

It is another object of my invention to provide a means controlled bysuch a knob at shut ofi the refrigerating system.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. 1 is a diagrammatical view of a refrigerating system illustratingmy invention;

Fig. 2 is a vertical secondary view of a refrigerator cabinet showing aportion of the control means for the refrigerating apparatus with thecontrol knob in No. 1 position;

Fig. 3 is a top view of a portion of the control apparatus shown in Fig.2 but with the control knob in off position;

Fig. 4 is a front view partly in section of the control apparatus shownin Figs. 2 and 3 but with the control knob in off position;

Fig. 5 is a sectional view along the line 55 of Fig. 3;

Fig. 6 is a sectional view along the line 6--6 of Fig. 3;

Fig. '7 is a top view of a modified form of control means with thetemperature adjusting mechanism and the control knob in No. 1 positionand the switch contacts in closed position;

Fig. 8 is a front view of the modification shown in Fig. 7;

Fig. 9 is a sectional View along the line 9-9 of Fig. '7;

Fig. 10 is a fragmentary top view similar to Fig. 7 excepting that theswitch contacts are shown in open position and the temperature adjustingmechanism is shown in No. 4 position;

Fig. 11 is a sectional view along the line I [-1 l of Fig. 7 showing thecontrol knob and adjusting means in No. 1 position; and

Fig. 12 is a sectional view along the line ll-l l with the control knoband adjusting means in No. 4 position.

Referring to the drawings and more particularly to Fig. 1, there isshown a refrigerating apparatus including a compressor 20 forcompressing the refrigerant and for forwarding the compressedrefrigerant through a supply conduit 2| to a condenser 22 where thecompressed refrigerant is liquefied and collected in a receiver 23. Fromthe receiver 23 the liquid refrigerant is forwarded through a supplyconduit under the control of a suitable expansion valve 24 to anevaporator 25 located within the food compartment 26 provided with meansfor freezing ice cubes or comestibles within an ice tray 21. Re-

frigerant within the evaporator 25 evaporates under reduced pressure andabsorbs heat from the ice trays and from the air in the foodcompartment. This vaporized refrigerant is returned to the compressorthrough a return conduit 28. The compressor is driven by an electricmotor 29 under the control of a control means, generally 7 designated bythe reference character 35 and illustrated diagrammatically in Fig. 1.This con trol means comprises a thermostat bulb Si in contact withportion of the evaporating means and provided with a volatile liquid orrefrigerant. The thermostatic bulb, although placed in con tact with theevaporating means, follows the temthermostat bulb 3i .is connected bytubing 32 to a metal bellows 33 which through snap acting mechanismopens and closes a set of switch contacts 35 located in one of thesupply conductors 35 of the electric motor 29. In series with the supplyconductor 35 and the switch contacts 3 3 is an overload protectingmechanism comprising a set of switch contacts 35, an electric heater 3]in series with the contacts 35 and 35 and a bimetal trip mechanism 38for opening the contacts 56 under the influence of the predeterminedamount of heat from the heatertl. The control means 35 operates tomaintain the proper temperature of the evaporating means and the foodcompartment.

Referring now more particularly to Figs 2 to 6 inclusive, for furtherillustration of one embodiment of my invention, there is disclosed asupporting platform 55 provided with supporting legs 4| resting upon aremovable partition wall 42 forming the top' wall of the foodcompartment 43'. Extending downwardly from the platform 45 is a tubularshaft 54 which extends downwardly through the removable wall structure52 which is provided with rubber sealing askets 45 for preventingleakage of air and moisture between the food compartment andthemachinery compartment 46 within which the control mean is located. Thelower end of the tubular shaft is provided with a rotatable manualcontrol knob or manipulator 41 which is provided with indications offand 6 which are clearly shown in Fig. 2, as well as the indications '1to 5 inclusive which extend around the other side of the control knobbetween the designations off and 6. As viewed in Fig. 2, the controlknob or manipulator, as well as the control apparatus, is shown in No. 1position.

Within the hollow shaft 45 there is provided a rod 48 provided with ared control button 49 at its lower end which serves to reset theoverload means and serves as an indicator when the overload means hastripped by dropping downwardly from this position shown in Fig. 2 sothat it is clearly visible and clearly indicates the tripping of theoverload means.

Referring now more particularly to Fig. 4, the upper end of the hollowshaft 44 is shown provided with a bushing 50 which is rotatably mountedwithin an aperture in the platform 40. This bushing is provided withflanges which extend oneither side of the platform 40 so as to permitrotation of the bushing 50 but to prevent vertical movement thereof. Thebushing 50 is fixed to the hollow shaft 44 by a set screw 5|. Theoverload control rod 48 extends upwardly through the bushing so and isconnected by a pin and set screw 52 at its upper end to a lever 53 whichis pivoted upon a screw 55 to a vertical bracket 55. This verticalbracket 55 at its upper end is pivotally connected by a pin M8 to acontact lever 55 carrying a contact 57 which cooperates with a springmounted contact 58.corresponding to the set of contacts 36 to open andclose the electric motor circuit. This contact lever 55 is normally heldin closed position by a bimetal strip 55 which is adapted to be heatedupon an overload by a nickel chromium wire heater 55 connected in serieswith the contacts 57 and 58.

At its lower end the bimetal strip 59 is connected to a pivot block 6!to which is also connected a bimetal compensating strip 52 which is heldby an adjusting screw 55 and a spring 5 5 at its free end and thusserves as an adjusting means. This bimetal strip 5! also acts as atemperature compensator for the bimetal strip 59 for compensating thebimetal strip 59 for the variations in room, and particularly themachine compartment, temperature. The lever 53 is provided with aninsulating portion 65 having pins 66 projecting therefrom on either sideof the contact lever 56, which supports the lever 53 and the rod '58when the contacts 51 and 58 are in closed position. pass through theheater 50, the bimetal strip 59 will bow to the 'left as shown in Fig.4, so (that its upper end moves out from under the lever 55 and permitsit to fall. This contact lever 56 is thus permitted to fall and the rod48 falls with it displaying the red button 49 within the foodcompartment 63. In order to reset the thermal overload mechanism, thebutton 49 is pushed upwardly thus causing one of the pins 66.110 raisethe contact lever 55 to permit the bimetal strip 59 to resume itsvertical position beneath the con tact lever 55. The projection of thisinsulating portion which carries the pins 66, during this time, engagesthe projecting end of the leaf spring carrying the contact 58 and holdsthe overload contacts open to prevent forcible operation of theapparatus under overload conditions.

The upper end of the bushing 50 is threaded and provided with a thin nut10 which is held from rotation by a hook-shaped member I! whose verticalportion holds one of the flats of the hexagonal nut Hi. The'hook-shapedmember H is provided with the apertures 12 and 13 which receive an arm Mextending from a top plate 15 provided with ears I6 pivotally connectedby a pin I1 to'a bracket 18 which extends upwardly from the metalplatform 40. Resting upon the bottom portion of the bracket 18 is ametal bellows 19 corresponding to the bellows 33 of Fig. 1 fastened tothe platform 40 by a nut and connected to a thermostat bulb, such asbulb 3|, by a tube 8| which corresponds to the tube 32.

At the upper movable end of the bellows there is provided a conical pin82 which is seated within the recess in the bottom side of a bellowsfollower 83 provided with ears which are pivotally con nected to thebracket 18 by the pin 84. Seated upon the bellows follower 83 is a lowerspring retainer 85 having a conical-pointed lower end which seats in arecess upon the top of the bellows follower 83. This lower springretainer 85 supports the lower end of a compression type coil spring 86whose upper end is retained by an adjustable upper spring retainer 81which-is threaded upon a pin 88 riveted to the top plate 15 to vary theinitial tension of the spring 86. This Should an excessive amount ofcurrent provides the ordinary factory-set range adjustment.

When the control knob ormanipulator 41 is turned, the thin nut I movesup and down upon the threaded portion of the' upper end of the bushing50 to permit raising or lowering of the hook-shaped member 'II and thefree end of the top plate and upper spring retainer 81 so as to vary thetension upon the spring 86 in order to control the expansion of themetal bellows I9.

Also pivotally mounted upon the pivot pin 84 is the main switch arm orlever 90 which at its free end has an insulating member 94 fastenedthereto by a bolt 96. This insulating member is provided with Vshapednotches 95 which receive knife edges at the ends of a wish-bone shapedmember 91 which is provided with a rubber silencer 98 which cooperateswith stop portions 99 formed on a bracket I00 fixed to the platform 40.These stop portions 99 are provided with tripping pins IOI which contactthe wish-bone shaped member immediately before tripping in.

order to control its tripping position. The wishbone shaped member isconnected at its closed end to a tension coil spring I02 which isconnected at its opposite end to an upstanding projection I03 formed ona contact lever I04 carrying a movable contact I05 which cooperates witha stationary contact I06, which set of contacts corresponds to the setof contacts. 34 shown in Fig. 1. This contact lever is pivoted at I01 tothe bracket I00. The insulating member 94insulates the control knob, thebellows, and the remainder of the refrigerating system from the currentcarrying contact lever I04.

The main switch arm or lever 90 is operated by the metal bellows I9 andthe bellows follower 83 through a resilient connection which includes ahook-shaped member I08 which hooks the bottom of a main switch lever 90and which extends upwardly through an aperture in the extension I09 ofthe bellows follower 83 upon which rests a small compression type coilspring IIO which surrounds the upper end of the hook-shaped member I08.The upper end of the spring III! is held by a cotter pin I II whichextends through the upper end of the hook-shaped member I08 andyieldingly connects the contact arm 90 with the bellows follower 83through an extension I09. At the opposite side the main switch lever orarm 90 isprovided witha downward extension 9| which is adapted to beengaged by a projecting foot 92 extending from the bushing 50 when thecontrol knob or manipulator 41 is turned to the off position. When thisprojecting foot 92 comes into engagement with the downward projection9I, the main switch arm 90 is forcibly moved downwardly and held in theoff position, thus holding the main switch contacts I05 and I06 in theopen position. The resilient connection between the main switch arm 90and the bellows follower under these conditions yields and preventsexcessive strain upon the switch arm 90 by permitting the bellowsfollower 83 to move upwardly without a corresponding movement of themain switch arm 90.

The bushing 50 is also provided with a cam II5 which when the controlknob is in No. 1 position cooperates with the end of a lever II 6pivoted at an intermediate point to an upwardly extending portion III ofthe bracket I8; The opposite end of this lever is connected to a tensiontype coil spring II8 which has its upper end connected to an eyelet atthe lower end of a pin I20 which extends through an aperture in thebellows follower 83 and has its upper end threaded into a sleeve I2Iprovided with a hexagonal head I22; This sleeve, which is pulleddownwardly by the tension spring I I8, is adapted to rest, upon thebellows follower when the main switch arm 90 and the bellows followerare in the upper portion of their normal movement but to be separatedfrom the bellows follower as shown in Fig. 5 when the main switch arm 90and the bellows follower 83 are in the lower portion of their normalmovement. When the bellows follower and the main switch arm 90 are intheir lower positions, the hexagonal head I22 is pulled down upon, andis adapted to rest upon the seat I23 provided with an aperture whichreceives the sleeve I2I. This seat I23 is formed from an upwardlyprojecting portion of the bracket I8. A set screw I24 extends into thehexagonal head I22 and serves to lock the threaded pin I20 within thesleeve I2I.

This mechanism provides the differential adjustment for the switch. Byturning the sleeve I2I by means of its hexagonal head I22 upon thethreaded pin I20 the tension of the differential spring H8 iscorrespondingly varied. Inasmuch as this spring affects only the upwardmovement of the bellows it provides a means for varying the pressure andtemperature limits between the opening and closing of the switchcontacts I05 and I08 and constitutes the ordinary factory-setdiiferential adjustment. This differential adjustment affects only theclosing pressure and temperature by increasing the tension upon thespring IIB, the open temperature and pressure limit for closing pressureand temperature limit is increased without affecting the lowertemperature limit. The opening and closing temperatures of the switchare also controlled by the control knob which through the medium of thepartially threaded end portion of the bushing 50 and the thin nut andthe compression spring 86 provide a limited range adjustment in additionto the factory-set range adjustment which beginning with No. 6 positionand turning the knob toward No. 1 position raises both the upper andlower temperature limits approximately the same amount, for exampleabout 2 or 3 F., but in the No. 1 position of the control knob, the camII5 also comes into play as previously described and through the mediumof the lever II6 provides an additional tension upon the differentialspring II8 which further raises the upper temperature limit. In thisposition therefore the differential between the upper and lowertemperature limits is widened as well as both temperature limits beingraised.

The upper temperature limit in No. 1 position is preferably madesuificiently high so as to insure defrosting during each cycle, whilethe lower temperature limit is made sufficiently low to insure adequatecooling of the food compartment to prevent food spoilage. For example, acut-in temperature of 40 F. and a cut-off temperature of 14 F. may beprovided in No. 1 position, while in No. 2 position the cut intemperature might be set at 28 F. and cut off temperature at 11 F. Inpositions 3 to 6 inclusive, both the cut in and cut off temperatures maybe lowered about 3" F. for each different position. The positionsnumbered 2 to 6 are employed to obtain freezing temperatures forfreezing ice and comestibles.

As explained before, when the control knob isturned to off position, thefoot 92 engages the extension 8| of the main switch arm 90 in order toforcibly open the main switch contacts and to hold them in this positionagainst the tension of the yielding connections provided by thehookshaped member I08 and the spring Ilil. It may be noted that duringthis time the lever II6 remains upon the cam I I but is not eiiectivewhile the control knob is in the off position since the movement of themain switch arm is prevented.

In Figs. 7 to 12 inclusive I have shown a modification of my invention.In this modification I have provided a fiat, rectangular base I58 ofinsulating material to which is attached by means. of the screw I5I abellows supporting bracket I52 which has a flange I53 at one endprovided with a notch I59 for supporting the fixed end of the metalbellows I55 which is connected to a tube I58 which connects with thethermostat mounted upon the evaporator or cooling unit. The opposite endof the bracket I52 is provided with an u-p-turned flange I5I which isadapted to be engaged when the bellows is extended or expanded anexcessive amount by a cap I58 seated upon the movable end of thebellows. Extending from the cap I58 is a rod I59 which is provided withashoulder I89 and a reduced portion I5I having a threaded end.

A pin I82 extends through the rod I59 and is received within a notch II59 formed in the main switch lever or arm I89 which is pivoted upon apivot screw I85 supported by a pivot'bracket I58. The main switch armI99 is held against the pin I52 by a compression type coil spring IIIIwhich extends between the cap I58 and a spring retainer I I89 whichseats upon the main switch arm I89.

The main switch arm I59 has a long upper portion I89, clearly shown inFig. 7, and a short lower portion I I9 which is parallel to the upperportion I69 and connected thereto by a web III. The long upper portionof the switch arm I89 isprovided with an insulating block III. at itsfree end p which is provided with, V-shaped notches I78 which receive apair of knife edges formed upon the legs of a, wish-bone shapedsecondary lever I19 whose movement is controlled and limited by the pairof stop pins I'I5 which are fixed to an adjusting member connected tothe base I59. This adjusting member varies the distance be tween theupper ends of the stop pins in order to provide a factory-setdifferential adjustment. The closed end of the wish-bone shapedsecondary lever is connected by a tension spring I78 to an irregularlyshaped contact arm III which is pivoted to the base upon'a pin I18. Thecontact arm II'I carries a contact I79 which cooperates with astationary contact I88 which is fastened to the base by a screw I 8I.The insulating block I72 serves to insulate the bellows, the arm I89,the manual controls, and the remainder of the refrigerating system fromthe current carrying portion of the switch.

As the pressure withinthe. bellows increases,

' toggle spring IIfi to the position shown in Fig. 10

so as to cause the main switch contacts I89 and I19 to be separated toopen the circuit to the compressor motor.

' ing the electric motor circuit whenthe dangerous How of electricenergy flows to the electric motor. This mechanism includes a bracket Imounted upon the base and carrying a spring brass strip.

I83 at its upper end'which is fastened at one end by a screw I 81. Thisbrass strip carries a contact I88 at its free end which cooperates witha second contact I89 mounted upon the end of a second brass strip I98fastened by a screw I 9I to a second bracket I92 fastened to a base. The

bracket I92 is connected to a source of electricity by a screw I 93which serves as a binding post.

Extending to the right of the screw I93 as shown in Figs. 7 and 8, is abimetal strip I99" which has its opposite end adjustably held in aflanged nut I95 and a lock nut I98 upon a stud I91 fixed to the base I59. The other end or the bimetal strip I 99 is connected/ to a rotatableround insulating member I98 which is formed with flats at either end towhich a bimetal strip I98 and a second bi-metal strip 299 is fastened byrivets. The bimetal strip I99 serves an adjusting means and a means forcompensating the second bimetal strip 289 for changes in machinecompartment and room temperature. The second bimetal strip 209 issimilar to the bimetal strip I99 but is provided on its bottom side witha serpentine heater wire 29I which is riveted thereto at one end andconnected to the screw 292 at the other end which fastens the bracketI85 to the base I59.

The free end of this second bimetal strip serves as a latch whichnormally holds the lower end of an insulatin bell crank lever 283 fromrotating in a clockwise direction about its pivot bolt 2% under theinfluence of the tension coil spring 205 which has one end connected toan ear at the lower endof the insulating bell crank lever 203 ahd itsopposite end connected to anear extendingfrom the jacket I92. The. otherend of the bell crank lever is provided with a knob 296 which is heldupon the top of the brass strip I86 immediately above the contacts I89and I89 by the second bimetal strip 28I so as to hold the contacts I89and I88 in closed position.

This overload mechanism provides a circuit from the bracket I92 throughthe brass strip I90, the contacts I89 and I88, the brass strip I85, thebracket I 85, and then through the serpentine wire heater to the secondbrass strip .and is then conducted through a flexible electricalconductor 201 to the contact arm III which carries the contact I19 whichcooperates with a stationary contact I88. When a dangerous or excessiveflow of electric current passes through this circuit the wire heater 28Iheats the second bimetal strip 208 sufilciently to cause it to bowdownwardly and release the bell crank lever 293 which rotates in aclockwise direction under the influence of, the spring 285 so as toraisethe knob 285 from the brass strip I88 to permitthe contact I88 to moveupwardly away from the contact I99. The brass strip I8 6 springsupwardly further than the brass strip I thus causing the contacts I 88and I89to be separated. The release of the bell crank lever 283 by thebimetal strip 290 permits this lever to be rotated clockwise underthemfluence of the spring 285 and causes this lever to engage a pin 299upon a T-shaped lever .2I8

adjustably connected to a vertical rod 2 which extends downwardlythrough a hollow shaft 2I2 which extends from the machine compartment2I5 in which the switch is located down through the top wall 2 I6 of therefrigerator cabinet. The top wall 2I6 is provided with a notch 2I1within the food compartment 2I8 and within this notch 2I1 is a controlknob 2I4 at the lower end of the hollow shaft 2 I2. Within the controlknob 2 I4 is a button 2 I9 which is connected to the lower end of therod 2I I. When the rod 2I I drops, the button 2I9 also drops andexhibits a red band which indicates the fact that the overload mechanismhas tripped.

The overload mechanism is restored to the normal closed position bypushing upwardly upon the button 2I9 which moves the rod 2 vertically.This moves the T-shaped lever 2I0 in a counterclockwise direction whichthrough the upper pin 209 rotates the bell crank lever 203 in -acounter-clockwise direction about the pivot bolt 204 while the lower pin208 bears upon free end of the brass strip I90 to hold the overloadcontacts I88 and I89 in open position during the entire resettingoperation. The counterclockwise -movement of the bell crank lever 203permits the bimetal strip 200 to return to its latched position in whichthe knob 206 holds the overload contacts in closed position.

The control knob 2I4 regulates the tempera-- ture of the evaporator andthe food compartment by adjusting the operation of the metal bellows andthe main switch contacts. The hollow shaft 2I2 upon which the controlknob 2I4 is mounted is provided with a flanged collar 220 at its upperend which is held within an aperture in a metal plate 22I fastened tothe base I50. This connection between the collar 220 permits rotation ofthe hollow shaft 2I2 but prevents vertical or axial movement thereof.The upper end of the hollow shaft 2I2 is provided with coarse threads222 upon which is threaded a serrated nut 223 which is normally heldfrom rotation by a coiled wire spring latch means 224 which is adaptedto engage in one of the notches provided in the periphery of the nut223. This wire spring latch means is coiled around the pin 225 which isfixed in a bracket 221 pivoted to the metal plate 22I. This spring latchmeans is prevented from rotating aboutthe pin 225 by the projecting end226 which is hooked into the pivoted bracket 221.

The pivoted bracket 221 has a forked, humped end portion 228 which restsagainst the bottom side of the nut 223. By turning the control knob 2and the cap 2I2, the nut 223 is moved upwardly or downwardly along theupper threaded portion 222 of the hollow shaft 2I2. Through its forkedend 228, the bracket 221 is pivoted about its pivot connection 229 withthe met-a1 plate 22l The pivoted bracket 221 has a second forkedprojection 230 which is provided with a pair of pins "I which restwithin depressions provided within a spring retainer 232.

This spring retainer 232 supports one end of a rather stiff compressionspring 233 which is supported at its other end by a second springretainer 234 which is seated upon a shoulder 235 formed at the beginningof the reduced portion of-the bellows rod I59 which is moved by the.

bellows I55. Within the heavy outer coil spring 233 is a light coilspring 236 which is held between an inner spring retainer 231 seatedupon the outer spring retainer 234 which in turn is seated upon theshoulder 235 and a second inner spring retainer 238 which is normallyseated upon a sleeve 239 which is threaded upon the threaded reducedportion of the bellows rod I59. The turning of the sleeve 239 upon thebellows rod I59 provides a factory-set differential adjustment. Normallythis inner spring 236 is inactive or ineffective and moves bodily withthe control rod I59 as shown best in Fig. 10.

However, when the control knob 2I4 is moved to No. 1 position of thecontrol knob 2I4, as shown in Fig. 11, the spring retainer 232compresses the heavy coil spring 233 a proportionate amount and in sodoing moves toward the bellows a sufficient distance to cause the nibs240 which are formed thereon to engage the inner spring retainer 238 ofthe light inner spring 236 only upon the outward movement of the bellowsI55 and the switch arm I64, thus providing an additional resistance tothe expansion of the bellows I55 which raises the cut-in or closingtemperature of the main switch contacts I19 and I80 in addition to thenormal increase provided by the further compressing of the heavy outerspring 233. This additional resistance provided in the No. 1 position bythe light inner coil spring 236 thus widens the differential.

The upper limit or cut-in point of the refrigerating cycles in thiscontrol position is thus increased to about 40 F. which is suflicient todefrost the evaporator and yet the cut-out point remains at a relativelylow point, about 14 F. This provides suflicient cooling of the foodcompartment to prevent food spoilage and yet permits the frost to meltfrom the cooling unit during each cycle. When the cold control knob ismoved to positions 2 to 6 inclusive, the outer spring retainer 232 isprogressively retracted and permits lower evaporator and boxtemperatures particularly for freezing purposes. In these positions theouter spring retainer 232 is sufficiently retracted so that the nibs 240will not engage the spring retainer 238 within the normal range ofmovement of the bellows I55, the bellows rod I59, and the switch armI64. This condition of operation is best illustrated in Fig. 12 in whichthe control knob 2 I4 is shown in No. 4 position. Thus, when the controlknob is in positions 2 to 6 inclusive, the light inner screw does notcome into play and the switch operates with the differential between theopening and closing of the switch contacts and the starting and stoppingof the compressor remaining the same and this is, of course, calledrange adjustment.

The control knob 2I4 is also provided with an vofi position whichcontrols the turning on and shutting off of the refrigerating system. Inor-' der to do this, the collar 220 is provided with a projection 242which when the control knob is turned to off position engages the lowerportion I of the switch arm I64 to forcibly move the switch arm I 64away from the pin I62 against the tension of the spring I81 in order toforcibly move the movable switch contact I19 to open circuit positionand to hold it there as long as desired.

In practice the switch and the refrigerating system are so set andadjusted as to provide the normal control in No. 2 position of thecontrol knob to obtain fully adequate refrigerating temperatures forboth the freezing of ice cubes and also for cooling the food compartmentsufliciently to prevent food spoilage as has been customary in the past.The temperature in this position is sufliciently low to providesomewhat-more than high to prevent or retard the accumulation of frostupon the evaporator and to reduce the current consumption, the controlknob is turned to No. 1 position which is just barely adequate orsometimes inadequate for ordinary freezing purposes, but which willsupply sufiicient refrigeration to the food compartment to prevent foodspoilage. When the evaporating means is suitably constructed, the switchand the refrigerator may operate ordinarily in No. 1 position whereinany frost accumulating will melt from the evaporator every cycle. Theevaporator may, of course, also be defrosted by moving the control knobto the off position to shut off the refrigerating system.

Thus I have provided a convenient control knob and thermal overloadcontrol which is accessible from the food compartment 218 and yet theswitch mechanism is located within the machine compartment where it isnot subject to the unfavorable moisture and freezing conditions presentwithin the evaporator and food compartments. The control knob throughits control of switch adjustment governs the continuous cycling of therefrigerating system to provide either temperatures sufficiently high todefrost the evaporator by a combined range and differential adjustmentor by a limited range adjustment to provide lower evaporator and foodcompartment temperatures. In addition, the control knob serves to shutbe the refrigerating system.

While the form. of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

l. A switch including meansfor opening and closing an. electric circuit,a bellows, a bellows follower operated by the bellows, said bellowsfollower having an insulating portion thereon provided with notches, andsnap acting mechanism cooperating with said notches for actuating saidfirst mentioned means.

2. A control switch including a pressure responsive means, a set ofswitch contacts, a memher connected to open and close said switchcontacts, spring means for normally holding said member and saidpressure responsive means in direct unitary operative connection tocause the member and the pressure responsive means to normally operateas a unit responsive to pressures, and manual operating meansindependent of said pressure responsive means and acting directly uponsaid member for opening said contacts.

3. A control switch including a pressure responsive means, a set ofswitch, contacts, snap acting means for opening and closing said switchcontacts with a snap action, a. member connected to said snap actingmeans to open and close said switch contacts through the interconnectionof the snap acting means, spring means for normally holding said memberand said pressure responsive means in direct unitary operativeconnection to operate said member responsively to changes in pressure,and manual operating means independent of said pressure responsive meansand acting directly upon said member to open said contacts. I

4. A snap acting switch means including a primary operating. member, asecondary member pivoted to the primary member, a pivotally mountedswitch contact member, said switch contact member extending in theopposite direction from the pivot from that of the secondary member,spring means connecting the free ends of said" switch contact member andsaid secondary member, abutment means for limiting the movement of thefree end of said secondary member, said secondary member and saidswitchcontact member being tripped when the pivot of the secondarymember crossesthe center line of the spring means, cushioning means forsilencing the contact of. the secondary member with the abutment memberwhen the secondary member is tripped, and means independent of thecushioning means for holding the free end of said secondary member inproper position im-- secondary member extends from its pivot, a coilspring connecting the free ends of the secondary member and said contactmember, said coil spring holding said knife edges of said secondarymember against the portion of the primary operating member, and abutmentmeans for limiting the movement of the free end of said sec ondarymember.

6. A snap-acting switch means including a primary operating member, asecondary member pivoted to said primary member, supporting means, aswitch contact member pivoted to said supporting means, spring meansconnecting said secondary member and said switch contact member, saidstationary means having means for limiting the movement of the free endof said secondary member, said secondary member and said spring contactmember being tripped when the pivot of said secondary member crosses thecenter-line of the spring means, cushioning means for silencing thecontact ofthe secondary member with the stationary means, saidstationary means having means independent of the cushioning means forholding the free end of said secondary member in proper positionimmediately before tripping.

7. A control switch including an electric circuit, pressure responsivemeans for opening and closing said electric circuit in accordance withchanges in pressure, overload means for opening the circuit underpredetermined current conditions, manually operable means forselectively cuit, pressure'responsive means for opening and closing saidelectric circuit in accordance with changes in pressure, overload meansfor opening the circuit under predetermined current condicating that theoverload means has opened the electric circuit.

9. A control mechanism including a member to be operated, a pressureresponsive means, adjustable spring means acting upon said pressureresponsive means for controlling the operation of said pressureresponsive means, an operating arm connected to operate said member tobe operated,

resilient means for connecting said pressure responsive means and saidoperating arm for normally causing said operating arm to move rcsponsiveto movements of said pressure responsive means, manual control means forselectively controlling said spring means and said operating arm, saidmanual control means having a. plurality of selective positions, meanscontrolled by said manual control means when in one of said selectivepositions for varying the tension of said adjustable spring means, andmeans controlled by said manual control means when in another operativeposition for positively controlling said operating arm independently ofthe movement of said pressure responsive means.

10. A switch including means for opening and closing an electriccircuit, a movable element for operating said circuit opening andclosing means, a range adjusting means for modifying the opening andclosing points of the switch with the differential between the startingand stopping points remaining the same, a differential adjusting meansfor controlling the differential between opening and closing points, anda common manual control member for changing the adjustment of both therange adjusting means and the diiferenti-al adjusting means.

11. Control apparatuscomprising an adjustable member movable in responseto'variations in value of a controlling factor between minimum andmaximum limits thereof, and means for automatically restricting andwidening said limits in response to adjustment of said member toaccommodate changes in conditions affecting said controlling factor.

12. Control mechanism comprising, in combination, means movable inresponse to variations in oneof the factors effecting the control,adjustable spring means resisting said movement, supplemental springmeans also resisting said movement, and means for simultaneouslyadjusting both of said spring means to vary the eifect thereof. 7

13. In a thermally actuable switch construction, a switch having amovable switch member, a thermostat associated with the switch memberexerting force tending to move the switch in switch closing direction inaccordance with thermostat temperatures, opposing yieldable meanscomprising a pair of yieldable elements disposed to oppose thermostatactuated movement of the switch member in switch closing directionand-to assist movement thereof in the switch opening direction, thethermostat effecting closing of the switch at a predetermined relativelyhigh temperature only and one of the yieldable elements effectingopening of the switch at a predetermined relatively lower temperature,adjusting means comprising an adjustably movable member movable througha range of movement, transmitting means for transmitting movement of themovable member to the yieldable elements, the transmitting means beingresponsive to vary the effectiveness of the first mentioned yieldableelement to change the predetermined switch closing and openingtemperatures at substantially the same rate through a part of the rangeof movement of the movable member, and through another part of its rangeresponsive to change the elfectiveness of the other yieldable element tochange the predetermined closing temperature.

14. In a thermally actuable switch construction, a switch having amovable switch member, a thermostat associated with the switch memberexerting force tending to move the switch in closing direction inaccordance with thermostat temperatures, a plurality of yieldableelements disposed to oppose thermostat actuated movement of the switchmember, the thermostat effecting closing of the switch at apredetermined relatively high temperature only, and the yieldableelements effecting opening of the switch at a predetermined relativelylower temperature, adjusting means comprising an adjustably movablemember movable through a range of movement, transmitting means fortransmitting movement of the movable member to one of the yieldableelements and responsive to adjustably change the efiectiveness thereofto change the predetermined switch closing and opening temperatures atsubstantially the same rate through a part of the movement range of themovable member, and through another part of its range, responsive tochange the efiectiveness of another yieldable element to change thepredetermined closing temperature at a greater, rate than the openingtemperature.

15. In a thermally actuable switch construction, a switch having amovable switch member, a thermostat associated with the switch memberexerting force tending to move the switch in closing directioninaccordance with thermostat temperatures, a plurality of yieldableelements disposed to oppose thermostat actuated movement of the switchmember, the thermostat effecting closing of the switch at apredetermined relatively high temperature only, and the yieldableelements effecting opening of the switch at a predetermined relativelylower temperature, adjusting means comprisingan adjustably movablemember movable through a range of movement, transmitting means fortransmitting movement of the movable member to one of the yieldableelements and responsive to adjustably change the eifectiveness thereofto change the predetermined switch closing and opening temperaturessubstantially without changing the temperature difierence, through apart of the range of movement of the movable member, and through anotherpart responsive to change the predetermined closing and openingtemperatures and the temperature difference therebetween.

16. In a thermally actuable switch construction, a switch having amovable switch member,

a thermostat associated with the switch member exerting force tending tomove the switch in closing direction in accordance with thermostattemperatures, a plurality of yieldable elements disposed to opposethermostat actuated movement of the switch member, the thermostateffecting closing of the switch at a predetermined relatively hightemperature only, and the yieldable elements effecting opening of theswitch at a predetermined relatively lower temperature, adjusting meanscomprising an adjustably movable member movable through a range ofmovement, transmitting means for transmitting movement of the .movablemember to one of the yieldable elements and responsive to adjustablychange the eiIectiveness thereof to change the predetermined switchclosing and opening temperatures substantially without changing thetemperature difference therebetween, through a part of the range ofmovement of the movable member, and through another part responsive tochange the predetermined closing and opening temperatures,

and to increase the temperature difference therebetween.

17. In a thermally actuable switch construction, a switch having amovable switch member,

a thermostat associated with the switch member exerting force tending tomove the switch in closing direction in accordance with thermostattemperatures, a plurality of yieldable elements disposed to opposethermostat actuated movement of the switch member, the thermostateffecting closing of the switch at a predetermined relatively hightemperature only, and the yieldable elements efiecting opening of theswitch at a predetermined relatively lower temperature,

providing a temperature difference therebetween, adjusting meanscomprising an-adjustably movable member movable through a range ofmovement, transmitting means for transmitting movement of the movablemember to one of the yieldable elements and responsive to adjustablychange the eifectiveness thereof to change the predetermined switchopening temperature \by substantially equal amounts for equal amounts ofmovement of the movable member over its entire range of movement, andresponsive to change the predetermined closing temmrature bysubstantially equal amounts for equal movements of the movable memberover a part of its range and by greater amounts for equal movecontrollerfrom a low temperature range to the defrosting range, a switch deviceassociated with ciated with said sensitive means to vary thedifferential of the. limiting temperatures or pressures maintained bythe controller in a manner to cause increase of the closed periods ofthe switch over the normal periods determined by the resilient means asthe range is raised, whereby increased refrigerating periods areobtained at the defrosting range and a food-preserving temperature ismaintained in the refrigerator during defrosting.

19. A control switch including an electric circuit, temperatureresponsive means for opening and closing said electric circuit inaccordance with changes in temperature, manually operable means forcontrolling the operation of said switch including a hollow shaft memberand a member extending through said hollow shaft member, a rangeadjustment means for'varying the average operating temperature of saidswitch, an auxiliary control for said switch, and means for connectingone of said members to said range adjustment means and the other memberto said auxiliary control.

20. A snap acting switch means including a toggle means, a set ofcontacts operated by said toggle means, operating means for said togglemeans, cushioning means for stopping the toggle means at one end of itsmovement, and durable accurate locating means independent of saidcushioning means for accurately locating the ing and closing points ofthe switch remaining the same, a differential spring for controlling the-difierential between opening and closing points, adjusting means foradjusting the tension of the difierential spring and a common manualcontrol member for changing the adjustment of the range adjusting meansand the tension of the differential spring.

' GEORGE C. PEARCE.

